The present invention is directed to a novel procedure to improve the performance of oxidation and ammoxidation catalyst and the resulting catalyst produced therefrom. In particular, the present invention is directed to a procedure to improve the performance of an ammoxidation catalyst in the production of acrylonitrile or methacrylonitrile by ammoxidation of propylene or isobutylene in fluid bed reactors. A well-known problem associated with fluid bed reactors is that a part of the catalyst is continually lost from the reactor by being entrained in the gaseous reactor effluent. For this reason, it is conventional to regenerate used or spent catalyst after an appropriate period of time. Applicants' invention is directed to a novel procedure which is applicable equally to (1) improving the initial performance of the ammoxidation catalyst or (2) regenerating the used or spent catalyst after the appropriate period of time.
U.S. Pat. No. 3,882,159 to Callahan et al discloses a method for regenerating used or spent molybdenum containing catalyst. Callahan et al. observed that molybdenumcontaining oxidation catalysts tend to lose molybdenum over time. Accordingly, Callahan et al. teach that when supported particles of molybdenum oxide are added to the molybdenum depleted catalyst in an operating reactor, some of the molybdenum on the particle is transferred back to the catalyst causing regeneration of the catalyst.
U.S. Pat. No. 4,052,332 to D'Amore et al. discloses another technique for regenerating a used or spent bismuth molybdate ammoxidation catalyst whose molbdenum content has been depleted through extensive use. In accordance with the D'Amore et al. technique, the catalyst is withdrawn from the reactor and impregnated with a solution of bismuth and molybdenum in an amount sufficient to make up preferably at least 90% of the molybdenum lost from the catalyst. Since bismuth is not lost, the added bismuth increases the original content of the regenerated catalyst.
Finally, U.S. Pat. No. 4,311,611 to Sasaki et al. discloses a regeneration process for antimony containing catalyst comprising treating the deteriorated or spent catalyst with hydrogen peroxide.
While each of these techniques described above is capable of regenerating spent ammoxidation catalysts, each has its own disadvantages. For example, the D'Amore et al. technique requires the catalyst to be withdrawn from the reactor. This means that either the reactor has to be shut down, or only a portion of the catalyst may be withdrawn at any one time. In either event, the ammoxidation procedure obviously loses efficiency. The Callahan technique, while allowing for the in situ regeneration of the catalyst, provides limited improvement in the spent catalyst. All of the previously discussed techniques have the additional disadvantage that they are directed to only one type of catalyst. Applicant's invention provides a significant advance in the procedures described above because it can be utilized with more than one type of catalyst. That is, applicants' procedure can be utilized in improving or regenerating various types of catalyst, including molybdate based catalysts and antimonate based catalysts. Accordingly, applicants' procedure has an adaptability or flexibility not found in the previously described processes.